Methods for Washing Fibrous Immobilized β-Galactosidase

Abstract

We studied ways of washing fibrous immobilized β-galactosidase (IMG) in a horizontal rotary column reactor and a horizontal washing machine. In the horizontal rotary column reactor, IMG was washed by stirring as the column rotated and by air bubbles entering through orifices in the hollow shaft. In the horizontal washing machine, IMG was lifted up to the top of the drum by rotation and was washed by the impact of its falling onto the surface of a buffer solution which was about 1/4 volume of the drum. The results were as follows: (1) In the bubbling method, hydrolysis of lactose in skim milk and washing of IMG were repeated in the horizontal rotary column reactor. The amount of protein attached to IMG was under 22μg/mg (IMG (dry)) till the 6th processing, but it increased rapidly after that. (2) The packing density of IMG in the horizontal rotary column reactor must be kept under 0.008g/cm³ to fluidize IMG completely. In this case, however, an enormous quantity of the buffer solution was needed, which was undesirable for practical operation. (3) Washing of IMG in the horizontal washing machine and hydrolysis of lactose was carried out for 36 cycles. The packing density of IMG in the washing machine was 0.024g/cm³. The amount of protein attached to IMG was kept under 20μg/mg almost every time and 71 to 80% of lactose was hydrolyzed during processing. From the above results, we found that the horizontal washing machine has a higher washing efficiency than the bubbling method in the horizontal rotary column reactor.